We will be developing a lineage map of the chick retina using a new technology based on retrovirus vectors. The retrovirus vectors are ideal markers for lineage mapping in that they reproducibly integrate into virtually any cell type in most mammalian and avian species. This integration feature allows for the marking of a cell and all of its progeny. We will construct vectors which encode histochemical markers in order to provide a facile means to identify infected cells in tissue sections, and develop a methodology for infecting and assaying chick embryos. The chick retina will be the primary organ which will be analyzed using this new technique. The retina is well described anatomically and functionally and should provide for easy access in both early and late development stages. We wish to assess the lineage relationships among the various neuronal and glial cell types within the retina. We will also investigate questions of lineage within the retinal ganglion cells of the retina in order to assess the role of lineage in the establishment of the retino-tectal map. If we are successful in these studies, the vectors and methods described here will allow for lineage mapping in virtually any tissue in most mammalian and avian species.